Excess volumes of binary mixtures of an octane isomer and a polar component

Abstract

We have measured V^E at 298.15 K for the systems formed by 2,2,4-trimethylpentane or n-octane or cyclo-octane, with chlorobenzene, 1,2-dichlorobenzene and 1,3-dichlorobenzene. The results can be qualitatively understood in terms of the p^* and free-volume contributions to the excess functions. However, the effects of polarity and of the shape of the molecules are not as clear as in other studies reported in the literature.

Whereas Deiters' equation of state fits the results of each system well, it does not predict the observed change in V^E when the octane isomer is changed. On the other hand, generalized van der Waals, and a lattice-with-holes model, correctly predicts such a variation, although the quantitative agreement is poor.